In the case of a single pipe through which a low temperature fluid such as LPG or LNG flows, a heat insulation structure in which a heat insulating material such as a foaming body covers an outer periphery side of the single pipe has been widely adopted. However, when a low temperature liquefied gas (such as liquefied helium, liquefied hydrogen, liquefied nitrogen, or liquefied oxygen) having an extremely low temperature flows through the single pipe, the above heat insulation structure is inadequate. Therefore, practically used is a vacuum heat insulation dual structure pipe in which: a vacuum layer is formed between an inner pipe and an outer pipe for preventing convective heat transfer; and a heat insulating effect by this vacuum layer is utilized.
For example, a supply pipe (low temperature fluid dual structure pipe) described in PTL 1 is constituted by a FRP inner pipe and a FRP outer pipe and adopts a heat insulation structure which prevents vaporization of liquefied helium flowing through the inner pipe in such a manner that: nonwoven fabric on which aluminum is deposited is wound around an outer peripheral surface of the inner pipe; and a vacuum layer is formed between the inner pipe and the outer pipe.
As with the above dual structure pipe, as a gas storage tank for storing the low temperature fluid, a vacuum heat insulation dual structure storage tank is generally known, which is constituted by an inner tank storing the low temperature fluid and an outer tank externally fitted to the inner tank with a space therebetween and includes a vacuum layer formed in the space between the inner tank and the outer tank.